1. Field of the Invention
The present invention relates to semiconductor devices in general and more specifically to a memory card having a resin-molded layer without a plastic card base and a process for making memory cards.
2. Description of the Prior Art
A conventional memory card includes a card base made of plastic material. A molded package containing a semiconductor chip is inserted in and attached to the plastic card base. The package typically includes a printed circuit board having contact pads thereon. A circuit pattern in and on the circuit board electrically connects the contact pads to the chip mounted on the opposite side of the circuit board. The contact pads provide an electrical connection between the memory card and a card reader.
FIG. 1 shows an exploded perspective view of one example of a known memory card 10. In FIG. 1, the memory card 10 includes a plastic card base 13 into which a package 11 fits. An adhesive tape 12 attaches the package 11 to the card base 13. The card base 13 has two recessed areas 15 and 17 sized to receive the package 11. One recessed area 15 receives a resin-molded part 14 of the package 11, and the other recessed area 17 accepts a circuit board 16 and the adhesive tape 12.
Since the memory card 10 has two main members, namely, the package 11 and the card base 13, the process for manufacturing the memory card 10 requires two separate sub-processes that fabricate the respective members and a following sub-process to combine the package 11 and the card base 13. The number of processing steps makes this conventional process complicated. In addition, the process has significant drawbacks when producing the memory cards in large quantities because each package should be separately combined with the respective card base. Further, the requirement for multiple members (the card base, the package, and the adhesive tape) leads to higher manufacturing costs.
Memory cards have been widely used in electronic devices such as digital cameras, personal digital assistants, musical instruments, voice recorders, facsimile machines, printers, scanners, word processors, game machines, PC cards, and the like. The general trend in devices using the memory card is to make the devices smaller, lighter, thinner, more reliable, and less expensive. Meeting this trend requires smaller memory cards, but reducing the size of the memory cards is difficult because of the structural limitations that the card base imposes.
The present invention provides a simpler and smaller memory card by eliminating the conventional card base. Further, the present invention provides a process for making multiple memory cards, simultaneously, simply, and inexpensively.
One embodiment of the present invention provides a process for making a plurality of memory cards. Each of the memory cards includes a plurality of contact pads through which the memory card communicates with an outside card reader. The process begins with a multi-substrate. The multi-substrate includes a plurality of unit substrates, each of which is for each corresponding memory card. Each unit substrate has first and second faces, circuit wiring on the first face, and the contact pads on the second face. The contact pads on each unit substrate electrically connect to the circuit wiring. Semiconductor chips are attached to the multi-substrate. At least one semiconductor chips is on each of the unit substrates and electrically connects to the circuit wiring of the respective unit substrate. A continuous resin-molded layer is formed on the multi-substrate. The continuous resin-molded layer covers the plurality of semiconductor chips and the circuit wirings, and extends over the plurality of unit substrates. Separating the unit substrates of the multi-substrate divides the continuous resin-molded layer into individual resin-molded layers on the respective unit substrates and thereby provides the memory cards. Each of the memory cards has a first surface formed from the unit substrate and an opposing second surface formed from the individual resin-molded layer.
In a preferred embodiment of the present invention, the multi-substrate includes at least two groups of the unit substrates. Each group includes unit substrates that are regularly and continuously arranged side by side. From one to eight of the semiconductor chips are on the first face of each unit substrate. One or more semiconductor chips directly attaches to the first face of each unit substrate. Optionally, semiconductor chips may be stacked on the attached chips. The formation of the continuous resin-molded layer may include setting the multi-substrate in a mold that has a cavity covering the unit substrates, injecting a molding resin into the cavity to form the continuous resin-molded layer, and taking the multi-substrate out of the mold after hardening the molding resin. Alternatively, when the multi-substrate includes at least two groups of the unit substrates, the mold may have at least two cavities, each cavity covering all unit substrates in a corresponding group. The process of the present invention may further include, after separating the multi-substrate, finishing the individual resin-molded layer of each memory card so that the individual resin-molded layer includes an inclined plane at one edge and a groove next to the opposite edge.
Another embodiment of the present invention provides a memory card including a plurality of contact pads. The contact pads are for electrical paths through which the memory card communicates with an outside card reader. The memory card includes a substrate having first and second faces, circuit wiring on the first face, and the contact pads on the second face. The contact pads electrically connect to the circuit wiring. The memory card also includes at least one semiconductor chip that is electrically connected to the circuit wiring on the first face. Moreover, the memory card comprises a resin-molded layer that is on the first face and covers the semiconductor chip and the circuit wiring. Accordingly, a first surface of the memory card is formed from the substrate, and an opposing second surface is formed from the resin-molded layer.
In a preferred embodiment of the present invention, side faces of the substrate and the resin-molded layer are coplanar. Furthermore, the resin-molded layer may have an inclined plane at one edge and a groove next to the opposite edge. The semiconductor chip may be a non-volatile memory chip. The contact pads may have wavy or stepped patterns for preventing data loss when the memory card is being inserted into or withdrawn from the card reader.